1. Field of the Invention
This invention relates to safety ski bindings and particularly to ski bindings of the type that includes a part attachable to a boot, a part attachable to a ski, and means for permitting controlled excursion of the part attached to the boot with respect to the part attached to the ski.
2. Description of the Prior Art
This invention represents an improvement over the ski safety device disclosed in my prior U.S. Pat. No. 3,871,674, issued Mar. 18, 1975. The safety ski binding disclosed in that patent comprises an elongated tread portion having means at the forward and rear ends for firmly clamping a ski boot thereto. A mounting plate for securing to the ski has upwardly projecting means interfitting with coacting means on the tread portion to permit rotary and lifting displacement of the tread portion with respect to the mounting plate, and pairs of tensioned cables extend from anchor points on the mounting plate spaced circumferentially with respect to the upwardly projecting means through guide means on the tread portion to tensioning means located in the tread portion.
In the embodiment disclosed in the patent, the coacting means on the tread member comprises a downward facing cylindrical cup that matingly engages the upwardly projecting means on the mounting plate. The guide means for the tensioned cables are pulleys mounted on the cylindrical outer surface of the cup, and the anchoring points for the tensioned cables are angularly displaced from the respective pulleys on a circle concentric with the upwardly projecting means and equal in diameter to the outer diameter of the cup. Any rotational displacement of the tread portion with respect to the mounting plate causes one of each pair of the tensioned cables to wrap around the circumference of the cup to produce increasing counter-torque as a linear function of the angle of rotation away from the equilibrium position.
In addition to rotational excursions, the safety binding of my prior U.S. patent also permits limited vertical excursions of the tread portion away from the mounting plate, such excursions being resisted by increasing tension in the cables as a function of the product of the spring rate and vertical excursion distance.
In subsequent tests of this binding, it has been found desirable to provide two modes of rotational excursion and also to provide means for releasing the skier's boot from the binding when the limits of excursion have been reached. Specifically, it has been found desirable to provide an initial rotational excursion mode in which the counter-torque remains substantially constant throughout a predetermined sector of rotation before the counter-torque begins to increase with increasing angle of rotation.